Research work is being carried out on secondary pathological mechanisms evoked in liver cells by primary lipoperoxidation due to carbon tetrachloride and bromotrichloromethane. Appearance of toxigenic oxidized lipids may play a role as an evoked secondary mechanism. Toxigenic lipids are generated in NADPH-microsome systems in vitro, and extracted into organic solvents. They are altered phospholipids; the toxigenic functional groups are probably peroxy functions of some kind. Our objective is to isolate and purify individual sub-classes of the toxigenic phospholipid mixtures by high performance liquid chromatography (HPLC), cleave off fatty acid side-chains, separate individual fatty acids (HPLC), and ultimately characterize the chemical nature of the toxigenic functional groups, by use of mass spectrometry. Fatty acids, cleaved from peroxidized lipids of rat liver microsomes, will cause contraction of smooth muscle strips cut from the stomach of the hamster or rat. These results indicate that peroxidatively altered lipids of liver cell microsomal origin have pharmacological properties. They may be related to prostaglandins. Our goal is to isolate the individual pharmacologically active fatty acids and to characterize their chemical nature. A disturbance in mechanisms responsible for maintenance of liver cell calcium homeostasis may be a pathological mechanism evoked secondarily by lipoperoxidation. In particular, CCl4 or BrCCl3-initiated lipid peroxidation may destroy the Ca2 ions-pump activity of the endoplasmic reticulum. We plan to test this hypothesis by initiating limited lipid peroxidation in isolated Fe2 ions-free rat liver microsomes with NADPH and CCl4 (or NADPH and BrCCl3) and studying such peroxidized microsomes for their capacity for Mg2 ions-ATP dependent sequestration of calcium ions. Possible effects of toxigenic and pharmacologically active peroxidized lipids on Mg2 ions-ATP dependent sequestration of calcium ions will also be studied. We propose to test the hypothesis that formation of phosgene from CCl4, and subsequent covalent binding of phosgene carbon to liver cell constituents may play a role in the mechanism or mechanisms of CCl4 toxicity.